Processes for the removal and recovery of minor elements in wet-process phosphoric acid

Abstract

In alternative embodiments, the invention provides processes and methods for the recovery or the removal of the so-called “Minor Elements” consisting of iron, aluminum and magnesium (expressed as oxides), from wet-process phosphoric acid using a continuous ion exchange approach. In alternative embodiments, use of processes and methods of the invention allows for the reduction of these Minor Elements with minimal phosphate losses and dilution in order to produce a phosphoric acid that is suitable for the production of fertilizer products such as world-class diammonium phosphate (DAP), merchant-grade phosphoric acid, superphosphoric acid, and other phosphoric acid products. Further, use of the invention would allow the use of lower grade phosphate rock or ore, which would greatly expand the potential phosphate rock reserve base for phosphate mining activities, and allow for better overall utilization of resources from a given developed mine site.

What is claimed is: 
     
       1. A method or process for the removal of one or more cationic metal minor element (ME) components, a mixture of minor element components, and/or a cationic metal impurity or contaminant, from a wet-process phosphoric acid comprising use of a continuous ion exchange system, comprising:
 (a) providing a wet-process phosphoric acid comprising a pretreated phosphoric acid solution, or a pretreated solution comprising a phosphoric acid, or a pretreated phos-acid feedstock, comprising high levels of one or more minor cationic element (ME) components, or a mixture of minor cationic element components, 
 and the pretreatment comprises reducing the amount of suspended solids content in an untreated wet-process phosphoric acid solution; 
 (b) providing a continuous ion exchange system comprising a strong cationic exchange resin or equivalent material, wherein the strong cationic resin or equivalent material is in the H+form 
 (c) providing a strong acid regeneration solution comprising a strong acid; 
 (d) applying the solution comprising a phosphoric acid or the phosphoric acid solution or the phos-acid feedstock of (a) to the strong cation exchange resin or equivalent material under conditions such that substantially most of the cationic metal impurities, contaminants, or minor element (ME) components, remain on the cationic exchange resin, 
 and an effluent acid solution is produced that has substantially lowered amounts of cationic metal impurities, contaminants, or minor element (ME) components, and substantially most of the cationic metal impurities, contaminants, or minor element (ME) components remain bound to the strong cation exchange resin or equivalent material; and 
 (e) removing the cationic metal impurities, contaminants, or minor element (ME) components, or eluting the cationic metal impurities, contaminants, or minor element (ME) components, from the strong cationic exchange resin or equivalent material using the strong acid regeneration solution to produce a cationic metal impurity-, contaminant-and/or minor element-containing effluent acid solution comprising substantially most of the cationic metal impurities, contaminants, or minor element (ME) components as an eluate, 
 further comprising treating the cationic metal impurity-, contaminant-and/or minor element-containing effluent acid solution with a ground phosphate rock or equivalent, to generate: 
 an acid solution comprising a water soluble phosphate, wherein the phosphate is derived from the ground phosphate rock or equivalent, and 
 a slow release phosphate material from the excess ground phosphate rock in a slurry form comprising the metallic impurities with the phosphate material. 
 
     
     
       2. The method or process of  claim 1 , wherein the treated ground phosphate rock or equivalent is used to produce a phosphate fertilizer product. 
     
     
       3. A method or process for the removal of one or more cationic metal minor element (ME) components, a mixture of minor element components, and/or a cationic metal impurity or contaminant, from a wet-process phosphoric acid comprising use of a continuous ion exchange system, comprising:
 (a) providing a wet-process phosphoric acid comprising a pretreated phosphoric acid solution, or a pretreated solution comprising a phosphoric acid, or a pretreated phos-acid feedstock, comprising high levels of one or more minor cationic element (ME) components, or a mixture of minor cationic element components, 
 and the pretreatment comprises reducing the amount of suspended solids content in an untreated wet-process phosphoric acid solution; 
 (b) providing a continuous ion exchange system comprising a strong cationic exchange resin or equivalent material, wherein the strong cationic resin or equivalent material is in the H+form 
 (c) providing a strong acid regeneration solution comprising a strong acid; 
 (d) applying the solution comprising a phosphoric acid or the phosphoric acid solution or the phos-acid feedstock of (a) to the strong cation exchange resin or equivalent material under conditions such that substantially most of the cationic metal impurities, contaminants, or minor element (ME) components, remain on the cationic exchange resin, 
 and an effluent acid solution is produced that has substantially lowered amounts of cationic metal impurities, contaminants, or minor element (ME) components, and substantially most of the cationic metal impurities, contaminants, or minor element (ME) components remain bound to the strong cation exchange resin or equivalent material; and 
 (e) removing the cationic metal impurities, contaminants, or minor element (ME) components, or eluting the cationic metal impurities, contaminants, or minor element (ME) components, from the strong cationic exchange resin or equivalent material using the strong acid regeneration solution to produce a cationic metal impurity-, contaminant-and/or minor element-containing effluent acid solution comprising substantially most of the cationic metal impurities, contaminants, or minor element (ME) components as an eluate, 
 further comprising evaporating the strong acid regeneration solution to selectively crystallize the cationic metal minor element fractions, wherein the crystallizing results in or produces an ME-sulfate salt. 
 
     
     
       4. A method or process for the removal of one or more cationic metal minor element (ME) components, a mixture of minor element components, and/or a cationic metal impurity or contaminant, from a wet-process phosphoric acid comprising use of a continuous ion exchange system, comprising:
 (a) providing a wet-process phosphoric acid comprising a pretreated phosphoric acid solution, or a pretreated solution comprising a phosphoric acid, or a pretreated phos-acid feedstock, comprising high levels of one or more minor cationic element (ME) components, or a mixture of minor cationic element components, 
 and the pretreatment comprises reducing the amount of suspended solids content in an untreated wet-process phosphoric acid solution, optionally by filtering; 
 (b) providing a continuous ion exchange system comprising a strong cationic exchange resin or equivalent material, wherein the strong cationic resin or equivalent material is in the H+form; 
 (c) providing a strong acid regeneration solution comprising a strong acid; 
 (d) applying the solution comprising a phosphoric acid or the phosphoric acid solution or the phos-acid feedstock of (a) to the strong cation exchange resin or equivalent material under conditions such that substantially most of the cationic metal impurities, contaminants, or minor element (ME) components, remain on the cationic exchange resin or equivalent material, 
 and an effluent acid solution is produced that has substantially lowered amounts of cationic metal impurities, contaminants, or minor element (ME) components, and substantially most of the cationic metal impurities, contaminants, or minor element (ME) components remain bound to the strong cationic exchange resin or equivalent material, 
 and optionally the produced acid solution is suitable for the production of fertilizer materials or di-ammonium phosphate (DAP), which requires a phosphoric acid that has a limited amount of cationic impurities; and 
 (e) removing the cationic metal impurities, contaminants, or minor element (ME) components, or eluting the cationic metal impurities, contaminants, or minor element (ME) components, from the strong cationic exchange resin or equivalent material using the strong acid regeneration solution to produce a cationic metal impurity-, contaminant-and/or minor element-containing effluent acid solution comprising substantially most of the cationic metal impurities, contaminants, or minor element (ME) components as an eluate, 
 wherein the strong cationic resin or equivalent material is either: 
 (a) designed as a continuous ion exchange system operated by restricting the flow of the strong acid regeneration solution in order to preferentially load one of the minor element materials on the resin, or 
 (b) in the strong acid regeneration solution. 
 
     
     
       5. The method or process of  claim 1 , wherein the strong cationic resin or equivalent material is designed as a continuous ion exchange system having one or more zones, and the continuous ion exchange system is operated in an up-flow mode to allow for periodic resin bed expansion and flushing of any accumulated solids from the resin. 
     
     
       6. The method or process of  claim 3 , wherein the concentration of the strong acid in the strong acid regeneration solution is increased,
 wherein optionally the strong acid in the strong acid regeneration solution is increased to concentrations in excess of about 40% for the sulfuric acid H 2 SO 4 ; optionally in excess of about 50% for the nitric acid or in excess of about 30% for the hydrochloric acid. 
 
     
     
       7. The method or process of  claim 3 , wherein:
 (a) the strong acid regeneration solution comprises a sulfuric acid (H 2 SO 4 ), a nitric acid (HNO 3 ) or a hydrochloric acid (HCI), 
 (b) the method of (a), wherein the sulfuric acid has a strength from about 5% to up to 98%, or in the range of about 20% to about 40% ; 
 (c) the strong acid regeneration solution comprises an acid having a strength from about 5% up to a concentrated level; or 
 (d) the strong acid regeneration solution comprises a strength up to about 35% , 40% , 50% , 60% , 70% , 80% , 90% or 98% , optionally in the range of about 62% when the strong acid regeneration solution comprises a nitric acid and about 37% when the strong acid regeneration solution comprises a hydrochloric acid. 
 
     
     
       8. The method or process of  claim 3 , wherein:
 (a) the phosphoric acid strength can range from about 12% to about 30% P 2 O 5 ; 
 (b) the phosphoric acid strength can range from about 18% to about 25% ; 
 (c) the phosphoric acid strength can range from about 42% P 2 O 5 up to about 54% P 2 O 5 ; 
 (d) the phosphoric acid strength can range from about 12% P 2 O5to about 18% P 2 O 5 ; or 
 (e) the phosphoric acid strength can range from about 25% P 2 O 5 to about 30% P 2 O 5 . 
 
     
     
       9. The method or process of  claim 3 , wherein the strong cationic exchange resin or equivalent material capable of binding the minor element (ME) components are selected from the group consisting of:
 (a) a Purolite SST-60™ material, comprised of gel polystyrene crosslinked with divinylbenzene (DVB) and a sulfonic acid functional group (Purolite, Bala Cynwyd, PA), or equivalents; 
 (b) a Purolite C-100™ resin, comprised of gel polystyrene crosslinked with divinylbenzene (DVB) and a sulfonic acid functional group (Purolite, Bala Cynwyd, PA) , or equivalents; 
 (c) a Dowex MSC 650™ material (Dow Chemical, Midland, MI) , or equivalents; 
 (d) a resin, a composition or a material, or a non-resin solid or a semi-solid material, comprising chelating groups, functionalities or moieties that can bind ME components, 
 wherein optionally that comprise a sulfonic acid functional group, iminodiacetic groups, chelating aminomethyl phosphonic acid groups or aminophosphonic groups, or similar chelating functionalities or moieties, 
 and optionally the compositions comprise beads, wires, meshes, nanobeads, nanotubes, nanowires or other nano-structures, or hydrogels; and 
 (e) any combination thereof. 
 
     
     
       10. The method or process of  claim 3 , wherein a cationic calcium (Ca +2 ) is also removed from the acid phase onto the resin. 
     
     
       11. The method or process of  claim 3 , wherein the phosphoric acid solution, the solution comprising a phosphoric acid, or the phos-acid feedstock, is first treated, or pre-treated, with a clarification process or a filtering process, or a clarification aid,
 and optionally the clarification process, filtering process or clarification aid comprises an activated clay, an activated carbon, an activated silica, or equivalents, or any combination thereof. 
 
     
     
       12. The method or process of  claim 3 , further comprising subsequently recovering the ME-sulfate salt, optionally as a marketable secondary/minor element fertilizer material. 
     
     
       13. The method or process of  claim 3 , further comprising recycling the concentrated sulfuric acid (H 2 SO 4 ) fraction to a primary extraction system. 
     
     
       14. The method or process of  claim 3 , wherein the method or process operates at a temperature:
 (a) in excess of about 140° F., but less than about 190° F., or 
 (b) between about 145° F. and about 160° F., 
 thereby resulting in a heated strong acid regeneration solution and a heated impurity-, contaminant- and/or minor element-containing effluent acid solution. 
 
     
     
       15. The method or process of  claim 14 , further comprising cooling the heated impurity-, contaminant- and/or minor element-containing effluent acid solution, wherein upon cooling sulfates crystallize from the solution as a mixed impurity-, contaminant- and/or minor element-sulfate product, thus producing a impurity-, contaminant- and/or minor element-free concentrated acid, or sulfuric acid (H 2 SO 4 ) and sulfate crystals. 
     
     
       16. The method or process of  claim 1 , wherein the cationic metal minor element components, or impurities or contaminants, comprise a cationic iron, optionally as a Fe +2  or Fe +3 , or a cationic aluminum, optionally in the Al +3  form, or a cationic magnesium, optionally as Mg +2 . 
     
     
       17. The method or process of  claim 1 , wherein the phosphoric acid solution, the solution comprising a phosphoric acid, or the phos-acid feedstock, is first treated, or pre-treated, with a clarification process or a filtering process, or a clarification aid. 
     
     
       18. The method or process of  claim 1 , further comprising:
 (a) treating the cationic metal impurity-, contaminant- and/or minor element-containing effluent acid solution with a lime and/or a lime-limestone mixture to precipitate the eluted minor elements as a hydroxide material; or, 
 (b) neutralizing the cationic metal impurity-, contaminant- and/or minor element-containing effluent acid solution to precipitate the eluted cationic metal impurity, contaminant, or minor elements as a hydroxide material, 
 and optionally further comprising separating the precipitated material for disposal to generate a precipitate-free water phase, optionally further comprising recycling the precipitate-free water phase. 
 
     
     
       19. The method or process of  claim 3 , wherein the cationic metal minor element components, or impurities or contaminants, comprise a cationic iron, optionally as a Fe +2  or Fe +3 , or a cationic aluminum, optionally in the Al +3  form, or a cationic magnesium, optionally as Mg +2 . 
     
     
       20. The method or process of  claim 3 , wherein the phosphoric acid solution, the solution comprising a phosphoric acid, or the phos-acid feedstock, is first treated, or pre-treated, with a clarification process or a filtering process, or a clarification aid. 
     
     
       21. The method or process of  claim 3 , further comprising:
 (a) treating the cationic metal impurity-, contaminant- and/or minor element-containing effluent acid solution with a lime and/or a lime-limestone mixture to precipitate the eluted minor elements as a hydroxide material; or, 
 (b) neutralizing the cationic metal impurity-, contaminant- and/or minor element-containing effluent acid solution to precipitate the eluted cationic metal impurity, contaminant, or minor elements as a hydroxide material, 
 and optionally further comprising separating the precipitated material for disposal to generate a precipitate-free water phase, optionally further comprising recycling the precipitate-free water phase. 
 
     
     
       22. The method or process of  claim 21 , further comprising:
 separating the precipitated material for disposal to generate a precipitate-free water phase, and optionally further comprising recycling the precipitate-free water phase. 
 
     
     
       23. The method or process of  claim 1 , wherein the pretreatment to reduce the amount of suspended solids content in an untreated wet-process phosphoric acid solution comprises filtering. 
     
     
       24. The method or process of  claim 1 , wherein the produced acid solution in step (d) is suitable for the production of fertilizer materials or di-ammonium phosphate (DAP), which requires a phosphoric acid that has a limited amount of cationic impurities. 
     
     
       25. The method or process of  claim 1 , wherein the treated ground phosphate rock or equivalent is used to produce a phosphate fertilizer product, optionally comprising a fast release P 2 O 5 ; a slow release P 2 O 5 ; secondary nutrients; and/or minor element nutrients. 
     
     
       26. The method or process of  claim 1 , further comprising recycling of the substantially cationic metal impurity-, contaminant- and/or minor element-free acid solution for use as a phosphoric acid solution, or a solution comprising a phosphoric acid, or a phos-acid feedstock of step  1 (a). 
     
     
       27. The method or process of  claim 3 , wherein the pretreatment to reduce the amount of suspended solids content in an untreated wet-process phosphoric acid solution comprises filtering. 
     
     
       28. The method or process of  claim 3 , wherein in step (d) the produced acid solution is suitable for the production of fertilizer materials or di-ammonium phosphate (DAP), which requires a phosphoric acid that has a limited amount of cationic impurities.